This disclosure relates to large parabolic aluminized reflector (PAR) lamps (e.g., PAR56 and PAR64, where the number following PAR represents the diameter of the widest part of the lamp in eighths of an inch), which lamps are widely used in the specialty market such as for accent and retail lighting, lobbies, corridors, etc.
Historically, this market employs an incandescent light source such as a halogen light source where the light source filament is oriented vertically (or parallel) to the center beam axis of the lamp. This orientation makes it easier to direct light with a reflector and improves optical control. The filament of the halogen light source is usually enclosed in a capsule to maintain the halogen cycle (tungsten evaporating from the filament, tungsten combining with the halogen (such as iodine, bromine, chlorine, or fluorine) and prevent the tungsten from contacting the lamp wall and blackening the wall surface). Halogen light sources are desirable because of the excellent color light but have a relatively short life and low efficacy.
Although quartz metal halide lamp sources may improve efficacy and life, these improvements are offset by the significant reduction in color quality. It is known that ceramic metal halide (CMH) light sources provide high efficacy, longer life, and good color. In other words, the ceramic metal halide light source combines the advantages of both halogen and quartz light sources with none of the significant drawbacks. In fact, CMH arctubes have been incorporated into smaller PAR reflectors (PAR20, PAR 30, AND PAR 38) for general, commercial lighting for several years. CMH lamps operate better in a horizontal position (as opposed to quartz lamps that are better operated in a vertical orientation as noted above).
Although it has been suggested to replace the quartz light source in a large PAR environment, there are physical constraints that preclude a simple substitution of one type of light source for another. For example, mounting a 150 Watt CMH arctube capsule into a large PAR reflector encounters the issue of size and mounting of the arctube, as well as a preferred direction of operation of the lamp. Specifically, a PAR56 reflector is wide and rather shallow. Thus, an elongated 150 W CMH lamp will not fit within the reflector, i.e., one end of the light source will extend axially outward from an outer end of the lamp. Moreover, mounting the 150 W CMH arctube light source along the axis of the lamp is not as desirable for optimal operation of the light source as noted above. It also becomes important to position the light source at the correct distance from the back of the reflector in order to eliminate or limit distortion from the ideal beam pattern.
In the environment of the even larger PAR64 lamp, heretofore incorporation of a 150 W CMH light source or arctube has simply not been adopted. There is slightly greater depth to the PAR64 reflector and thus the elongated 150 W CMH light source capsule will fit in an axial direction, that is, along the lamp axis. However, seemingly there has been no introduction of the 150 W light source into the PAR64 market.
Thus a need exits to create a large PAR specialty lamp (on the PAR56 and PAR64 scale) with attributes such as excellent color, efficacy, life, and accurate location of the light source in the reflector.